PowerApp/SharePoint Vs .NET/SharePoint Vs .NET/SQL

We want to start a new project for managing ISO process documents with approvals and custom permissions. the system need to have the following main characteristics :-

1. Secure the back-end
2. Server-side and Client side validation

now we have 3 approaches to develop the system:-

1. PowerApp/SharePoint
2. .NET/SharePoint
3. .NET/SQL

now i found the following prons & Cons for each approach:-

1. PowerApp/SharePoint

• Pros
  • fast development
  • built-in connectors
• Cons
  • user can access the SharePoint lists directly and bypass and validation on power apps
  • Power apps validations and formulas do not apply on the server, they only provide client side validation

2. .NET/SharePoint

• Pros
  • we can secure the SharePoint lists to only be accessible by a Azure AD app, and define the business logic using a server-side technology (.net)
  • we can define the client side validation using java/script
• Cons
  • can not find any drawbacks only that it needs more time for development

3. .NET/SQL

• Pros
  • we can secure the back-end and access the SQL using a service account
  • we can define server-side & client-side validations
• Cons
  • more time to develop
  • we will need to create a document management system from scratch

so can anyone advice on this ? am i pointing out the pros and cons correctly? or i am missing something?

Thanks